1. Field of the Invention
The present invention generally relates to hydrokinetic torque coupling devices, and more particularly to a hydrokinetic torque coupling device including a turbine-piston lock-up clutch for mechanically coupling driving and driven shafts.
2. Description of the Related Art
Generally, vehicles with automatic transmissions are equipped with a hydrokinetic torque coupling device for fluidly coupling the driving shaft of an engine to a driven shaft of a transmission. Lockup clutches are known for mechanically coupling the driving and driven shafts under certain operating conditions. Lock-up clutches and their operation are described in, for example, U.S. Pat. No. 8,276,723 and U.S. Pat. No. 7,191,879.
Depending on conditions, when the hydrokinetic torque coupling device is transmitting the movement through lock-up, the action of the transmission fluid generates axial forces, which are moving the turbine-piston away from the impeller, especially in coasting conditions of the motor vehicle when the transmission is at higher rotational speed than the engine. These conditions occur in downhill driving, for example. These forces vary depending on various factors, such as the speed and torque. Under some stable or transient conditions, these forces could move the turbine-piston away from the impeller and untimely or prematurely disengage the lock-up in unexpected circumstances, when it is not desires. This can also create a load that unable to engage the lock-up in coasting condition of the motor vehicle.
While hydrokinetic torque coupling devices with lock-up clutches have proven to be acceptable for vehicular driveline applications and conditions, improvements that may enhance their performance and cost are possible.
As taught hereinbelow, such improvements may derive from, for example, reducing the spatial requirements of components of the hydrokinetic torque coupling device and/or consolidating functions of two or more components into a single component.